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Why weird dreams may help us learn

Researchers simulated the cortex during three distinct states: wakefulness, non-REM sleep and REM sleep.

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Healthy sleeping concept. Pleased well slept woman in beige pajama embraces soft pillow keeps eyes closed feels peaceful and comfortable flies in air against brown background sees sweet dreams.
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By Danny Halpin via SWNS

Weird dreams may help our brain consolidate our experiences and learn from them, a new study has shown.

The importance of sleep and dreams for learning and memory has long been recognized, as has the impact a single restless night has on our cognition.

Lead author of the study doctoral student Nicolas Deperrois, publishing in the Human Brain Project, said: “What we lack is a theory that ties this together with consolidation of experiences, generalization of concepts and creativity.”

That connection may be the crazy dreams we experience in REM sleep, the stage of sleep when the brain is most active.

During the other phase of sleep, non-REM, the brain replays the sensory stimuli we experience while we are awake and spontaneous bursts of brain activity produce vivid dreams in REM sleep.

To examine how each phase affects learning, the researchers modeled simulations of the brain cortex, introducing elements of unusualness in the artificial dreams by taking inspiration from a machine learning technique called Generative Adversarial Networks (GANs).

In GANs, two neural networks compete with each other to generate new data from the same dataset, in this case a series of simple pictures of objects and animals.

The system produces new artificial images which look superficially realistic to humans.

Researchers then simulated the cortex during three distinct states: wakefulness, non-REM sleep and REM sleep.

During wakefulness, the model is exposed to pictures of boats, cars, dogs and other objects.

In non-REM sleep, the model replays these pictures with some occlusions.

REM sleep creates new GANs, generating twisted but realistic versions and combinations of boats, cars, dogs, etc.

To test the performance of the model, the researchers used a machine called a classifier which evaluated how easily the identity of the object can be read from the cortical representations.

Senior author and leader of the research team Dr. Jakob Jordan at the Department of Physiology, University of Bern said: “Non-REM and REM dreams become more realistic as our model learns.

“While non-REM dreams resemble waking experiences quite closely, REM dreams tend to creatively combine these experiences.”


Interestingly, it was when the REM sleep phase was suppressed in the model, or when these dreams were made less creative, that the accuracy of the classifier decreased.

When the non-REM sleep phase was removed these representations tended to be more sensitive to sensory fluctuations.

According to this study, wakefulness, non-REM and REM sleep appear to have complementary functions for learning: experiencing the stimulus, solidifying that experience and discovering semantic concepts.

Mr. Deperrois said: “We think these findings suggest a simple evolutionary role for dreams, without interpreting their exact meaning.

“It shouldn’t be surprising that dreams are bizarre: this bizarreness serves a purpose.

“The next time you’re having crazy dreams, maybe don’t try to find a deeper meaning – your brain may be simply organizing your experiences.”

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